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Algae detection?

My recent shock treatment for recurrence of Algae (May 9) after my first inadequate shock experience was a fantastic success resulting in the cleanest clearest pool I have ever seen.

Did the OCLT as outlined and all was good.

Since then I got the CYA up to a bit over 30

Present tests are:

FC 4
CC 0
PH 7.2
TA 70
CH 180
CYA 34

BUT

A few days ago I took out the trichlor Puck cause the FC was getting high and forgot to put it back in for a day. Big rain came and FC got down to 2. Greenish Yellow dust started appearing on floor. I brushed the whole thing and backwashed the filter…then checked the CC again to see if that changed it (stirring up the dust) but it still read 0.

My Question is: Is there a way to test and determine if this is algae or dirt/dust from roof screen (It is a screened Pool). Like an OCLT test to indicate that there is Algae eating up the Chlorine? I realize that it will become obvious in a day or two if it is back again but if I can determine if it is algae I can start the shock now and get done sooner. It was darker and thicker on the deep end which is the opposite of what I read about Mustard Algae formation symptoms.

Re: Algae detection?

This is a perfect situation for using the OCLT. If there is algae in the pool it should show up on the test.

CC almost always stays at zero when you have algae, so that is not a useful indicator.

Hi Jason, was just following along this thread and was curious why you say CC almost always stays at zero with algae, isn't that one of the conditions we're testing for when SLAM'ing? My thought was the presence of CC's meant you were killing algae or something, so it should show up as greater than zero, no?

Re: Algae detection?

CC are broken down by the FC and the sun, so you may never actually see high levels. This is why the low CC is not the only criteria and there are 3 separate things that you must pass to know you are down with a SLAM.

Re: Algae detection?

Strangeness…

OCLT shows no loss…
in fact if anything it show FC gain!

I know that sounds like poor testing but I was especially careful even to the point of using 25ML of water for the FC test and scraping the DPD spoon with a straight edge for accuracy and last night it took 19 drops to clear the water then 20 drops this AM.

I realize that is probably an irrelevant difference but how can you lose 0 PPM overnight?

Re: Algae detection?

One drop is well within the tolerance of the test. You didn't blow it.

16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!